SC-226 MEETING MINUTES Working Group JANUARY 14 ... - RTCA

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RTCA Paper No. 021-13/SC226-010 February 6, 2013 a relaxed noise requirement will not incumber intelligibility. The following language is being added to section 2.5.5 (c). (2) Subparagraph 2.4.11.1 - Audio Noise Without Signal (3) Paragraph 2.4.15 - Listening Test The equipment shall be subjected to the test conditions, as specified in RTCA/DO-160x, Section 8 .0. Exception: The following test level shall apply: For Audio Noise Without Signal, when tested in accordance with the test procedures in subparagraph 2.8.2.11.1, the level of the noise output of the system shall be at least 30 dB below the rated output of the system. 9th item of discussion: EASA deviations Deviations reviewed: EASA Deviation ETSO.DevP.17.pdf (Deviations requests #17 for an ETSO approval for CS-ETSO applicable to C57a (Headsets and Speakers) Consultation Paper) EUROCAE ED-18 specifies: Using the resistor substitution method, the equipment impedance at 1000 Hz shall be within ± 20% of the manufacturer’s rated impedance, which shall be between the limits of 150 Ωand 600 Ω Note Some general aviation avionics equipment may require the use of headsets with only 600 Ω impedance. Use of lower impedance headsets could result in damage to such avionics equipment. Therefore, headsets which have an earphone circuit impedance other than 600 Ω± 20% shall include in their installation instructions a caution stating the following: “Damage could occur to avionics equipment by the use of these headsets if the equipment was manufactured for use with only 600 Ω headsets. If in doubt, consult the avionics equipment manufacturer.” Page 8 of 20
RTCA Paper No. 021-13/SC226-010 February 6, 2013 Industry: Some aircraft manufacturers require headsets with impedance that shall be between the limits of 8 Ω and 32 Ω± 20%. An equivalent level of safety is provided limiting the use of headsets with low impedance in the aircraft or helicopters that require low impedance. SC226 committee response: The committee has addressed the use of 8 ohm and 50 ohm (representative of multiple 150 ohm) headsets connected in parallel. 8 ohm is now considered within the revised standard as “low impedance”, 600 ohm is now considered “high impedance” and 150 ohm is considered “commercial aviation impedance” headsets. The committee knows of no application of 32 ohm headsets being used in cockpit communication applications. 32 ohm headsets that the committee is aware of are typically consumer style headsets such as those used in the airline passenger cabin for music listening purposes, or those sold on the consumer market for IPOD music players. As such, 32 ohm headsets are not deemed appropriate for coverage by the revised standards. On the subject of damage to equipment occurring due to the use of low impedance headsets on a system intended for high impedance headsets, the committee considers that the standard also has a requirement for a short circuit test that is intended to insure the equipment is protected against damage due to low impedances being inadvertently connected. However, the committee also considers that there could be legacy equipment still in use within aircraft that may not have been required to meet the short circuit test contained in previous standard DO-170 or current standard DO-214 and as such, the note below DO-214 section 2.3.5.2 still applies. Note as follows: Some general aviation avionics equipment may require the use of headsets with 600 Ω impedance only. Use of lower impedance headsets could result in damage to such equipment. Therefore, headsets which have an earphone circuit impedance other than 600 Ω ±20% shall include in their installation instructions a caution stating the following: "Damage could occur to avionics equipment by the use of these headsets if the equipment was manufactured for use with 600 Ω headsets only-if in doubt, consult the avionics equipment manufacturer." EASA deviation ETSO.DevP.27.pdf Deviations requests ETSO.Dev.P027 for an ETSO approval for CS- ETSO applicable to Headset including Microphone (ETSO-C57a, C58a) Consultation Paper SC226 committee response: To address headset cord connector pull out the following note has been added to the standard section 2.2.8.3 and 2.3.8.4: Note: The earpiece-cord fastening for the headset will be subject to less amount of steady pull as the headset is not fixed at the head and the headset is not connected to a fixed mounted panel. Page 9 of 20
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SC-226 MEETING MINUTES Working Group JANUARY 14 ... - RTCA

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